In the making of glass, glassmaking materials are provided into a glassmelting furnace and melted into molten glass which is then poured into molds to produce products such as, for example, glass bottles. The glassmaking materials include batch oxidizers such as salt cake (calcium sulfate, CaSO.sub.4) and niter (sodium nitrate, NANO.sub.3, and potassium nitrate, KNO.sub.3) in order to control the redox state of the glass.
The reaction of the oxidizers with the molten glass results in the generation of sulfur oxides (SOx) and nitrogen oxides (NOx) which are significant pollutants.
The glassmaking materials are melted in the furnace by heat provided by the combustion of fuel and oxidant. The combustion reaction also generates combustion reaction products which include primarily water vapor and carbon dioxide but also may include carbon monoxide, nitrogen, unburned or incompletely burned fuel, and oxygen. Water vapor resulting from the combustion reacts with alkali oxides in the molten glass to form alkali hydroxides which vaporize out from the molten glass. These alkali hydroxides, such as sodium hydroxide, NaOH, react with furnace refractory walls and cause refractory corrosion, and, further react in the flue passage after the furnace with sulfur dioxide, SO.sub.2, and oxygen to form sodium sulfate, Na.sub.2 SO.sub.4, and other sulfate and sulfite compounds which form particulates and often require expensive electrostatic precipitators or baghouses to ensure that they are not emitted to the atmosphere.
It would be very desirable to provide a glassmelting method wherein volatilization of alkali species is reduced and the generation of particulates, SOx and NOx is reduced so that electrostatic precipitators or baghouses need not be employed while still meeting environmentally safe levels of particulate and other emissions.
Accordingly it is an object of this invention to provide a glassmelting method which can operate effectively without generating high levels of particulates, SOx and NOx.
It is another object of this invention to reduce the volatilization of batch oxidizers and other fining agents from the molten glass batch during glassmelting.